What caused the significant increase in Atlantic Ocean heat content since the mid-20th century?

This new paper from Lee et al just published in GRL has an answer. It seems warm water is being transported from the Indian Ocean via the Agulhas leakage.

Figure 2B time series of the simulated AMOC index (maximum overturning streamfunction) at 30°S obtained from EXP_ CTR. The green line in Figure 2b is obtained by performing a 11‐year running average to the AMOC index.

Abstract:

As the upper layer of the world ocean warms gradually during the 20th century, the inter-ocean heat transport from the Indian to Atlantic basin should be enhanced, and the Atlantic Ocean should therefore gain extra heat due to the increased upper ocean temperature of the inflow via the Agulhas leakage. Consistent with this hypothesis, instrumental records indicate that the Atlantic Ocean has warmed substantially more than any other ocean basin since the mid-20th century.

A surface-forced global ocean-ice coupled model is used to test this hypothesis and to find that the observed warming trend of the Atlantic Ocean since the 1950s is largely due to an increase in the inter-ocean heat transport from the Indian Ocean. Further analysis reveals that the increased inter-ocean heat transport is not only caused by the increased upper ocean temperature of the inflow but also, and more strongly, by the increased Agulhas Current leakage, which is augmented by the strengthening of the wind stress curl over the South Atlantic and Indian subtropical gyre.

Brian H says:
September 8, 2011 at 12:36 am
Then the Indian Ocean, which is smaller than the Atlantic, must be cooling drastically?
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I seem to recall from a piece Bob Tisdale posted here, that La Nina isn’t always the opposite of El Nino. The Indian ocean basin warms during both, and only cools when ENSO is neutral. As the period in question here saw less neutral conditions than the norm this could be the root cause of the warming.

Sorry, what leakage? They always choose words carefully. The Agulhas current is a massive warm current, it flows round Africa and overwhelms/mixes with the Antarctic upwelling and forms the Benguela current heading north in the Atlantic.

The only leakage in this uniform flow system is the weak counter current close to the coast that flows north back into the Indian Ocean.

Apologies for repeating this in more than one thread but it is relevant in each case.

It seems to be a little more complicated than clouds simply being a negative or positive feedback because latitudinal cloud distribution is also very important and the oceanic response to cloudiness changes confounds the initial expectation. Hence the significant rise in Atlantic Ocean heat content since the mid 20th century.

As I explain below the solar input to the tropical oceans increases when the sun is more active and it takes a while for that energy to circulate round the globe from the Pacific and into the Atlantic where it hangs around for quite a while because of the bottleneck in flow into the Arctic Ocean.

What I think happens is that for whatever reason the atmosphere expands when the sun is active and contracts when it is inactive.

In the process the temperature of the stratosphere and mesosphere changes oppositely to the sign of the temperature change in thermosphere and troposphere.

The effect is to draw the tropopause upward when the sun is active and push it down when the sun is less active. Globally averaged of course.

The outcome is latitudinal shifting of all the components of the surface air pressure distribution which changes the sizes and positions of the climate zones.

That changes the energy budget via the speed of the water cycle AND cloud quantities because that process changes the length of the air mass boundaries which is where mixing occurs to produce clouds.

So an active sun tries to COOL the system by changing the structure of the atmosphere to let energy OUT of the system FASTER via the higher tropopause but in the process cloud bands are drawn poleward to let more energy into the oceans in the tropics which offsets the faster energy loss to space.

So the cloud changes provide an indirect negative (warming) response to counter the direct solar cooling effect via the coolr stratosphere and mesosphere.

The position regarding bottom up effects from periodically faster energy release from the oceans or more energy in the air from more GHGs is different. In that case the extra warmth at lower levels pushes the tropopause up as before and in that case the increased energy into the oceans is a positive feedback. However the poleward shift of the surface air pressure systems accelerates the speed of energy transfer to space which is a negative response sufficient to cancel out both the extra energy from the oceans or GHGs AND the extra solar energy into the system.

Thus whatever changes the vertical temperature profile of the atmosphere from above or below will cause cloudiness changes that then exert a negative response either by adjusting energy flow into the oceans or by adjusting energy flow out to space as necessary to maintain equilibrium and what we then experience is shifting climate zones as the speed of energy flow through the system varies.

That is a neat solution to the problem.

It is the vertical temperature profile of the atmosphere that is key whether caused by top down solar effects or bottom up oceanic or GHG effects because that then causes the cloudiness changes.

It sounds complex and it is but it is no more complex than it needs to be to fit observations.

Brian H, tut! Where is your global warming theory text book. The heat from the Indian Ocean comes from the Pacific Ocean which comes from the Atlantic Ocean which is warmer because of the heat from the Indian Ocean. I ran it through my Scalectrix model car set and it came right back to the start. Proof that all cars in the world finish up where they started.

Variations in Agulhas leakage may explain some of the difference between the South Atlantic and Indian Ocean OHC, and would help to explain why South Atlantic OHC has flattened in recent years…
…while the Indian Ocean OHC has continued to rise:

But it does not explain why the rise in North Atlantic OHC was double that of the South Atlantic and almost 4 times higher than the Indian Ocean:
It also does not explain why North Atlantic OHC has dropped so drastically since 2005:

Lee et al (2011) opens their concluding Discussions (page 5) with:

“Obviously, there remain many crucial questions. One such question is the role of basin‐scale low‐frequency climate variability such as the Atlantic multidecadal oscillation (AMO) and the Pacific decadal oscillation on the differential inter‐ocean warming. In particular, the AMO, which arguably results from the natural oscillation of the AMOC driven in the North Atlantic sinking regions [e.g., Knight et al., 2005; Lee and Wang, 2010], may have directly contributed to the rapid warming of the Atlantic Ocean since the 1950s.”

The President of the Sychelles blamed the recent shark attacks on the water temperature in the area falling so attracting the more aggressive sharks to appear. So maybe there is some milage in this theory.

Consistent with this hypothesis, instrumental records indicate that the Atlantic Ocean has warmed substantially more than any other ocean basin since the mid-20th century.

A surface-forced global ocean-ice coupled model is used to test this hypothesis and to find that the observed warming trend of the Atlantic Ocean since the 1950s is largely due to an increase in the inter-ocean heat transport from the Indian Ocean.

Right, run it through a PlayStation and call the exercise an experiment. If actual observations are consistent with the hypothesis, doesn’t that mean it’s the model that’s being tested? And they back this with a “simulated AMOC index” and a “simulated heat budget.” Why not cite actual observations of Indian Ocean heat content?

John Marshall says:
September 8, 2011 at 2:44 am
The Indian ocean is 140m higher than the Atlantic but that is due to the shape of the planet and gravity.
=================================================================== No wonder the slow boat to China took so long if it had to climb up an 140m hill.

Grey lensman – as someone who has swum on both sides of the African subcontinent i would like to point out emphatically that the Agulhas does not overwhelm the Antarctic upwelling to form the Benguela. The Benguela current is the upwelling driven by prevailing winds-the sea is colder off the Namibian coast than further south. The desert climate has remained bonedry throughout the period.

Stephen. The president of the Seychelles needs a few stern words from Trenberth about going off message. Perhaps a resignation is in order.

Is the increase in Atlantic temperatures involved in the continuing low level of arctic summer ice? Is there much heat transport across the Equator? My geography lessons showed two very different circulations, north and south. I would like to have met the sailors (?) who kept such a fastidious record of temperatures in the Southern Oceans from 1870 into the 1900’s. Would it not be better to use temperature as an indicator (which is reality..see Al Gore) rather than “heat content” which is a cobbled together modelling invention?

Consistent with this hypothesis, instrumental records indicate that the Atlantic Ocean has warmed substantially more than any other ocean basin since the mid-20th century.

A surface-forced global ocean-ice coupled model is used to test this hypothesis and to find that the observed warming trend of the Atlantic Ocean since the 1950s is largely due to an increase in the inter-ocean heat transport from the Indian Ocean.

Right, run it through a PlayStation and call the exercise an experiment. If actual observations are consistent with the hypothesis, doesn’t that mean it’s the model that’s being tested? And they back this with a “simulated AMOC index” and a “simulated heat budget.” Why not cite actual observations of Indian Ocean heat content?

Distribution of heat is important. Warmer Atlantic water in the near-Arctic regions means greater evaporation there. The greater evaporation places greater amounts of water vapor into the Arctic atmosphere. That increase may, via water vapor’s greenhouse effect, trap more heat in the Arctic and thus raise the atmospheric temperature. Perhaps some of the observed higher temperatures in the Arctic are due to this.

I have to agree with LJHills – having swum on the False Bay (Indian Ocean/Aghullas Current) side and in the Atlantic on the other side of the Cape Peninsula, the water temperature is considerably lower in the Benguela water … I made the mistake of diving into it and almost bounced. That side is COLD! In fact the meeting of the two currents at Cape Point is clearly visible and the Benguela side is darker in hue. If either is “overwhelmed” then it is the Aghullas, but it is, in fact, deflected southward at this point, something which can be measured by Radio Bouys. No doubt some of the warm water is carried north by the Benguela at the meeting point, but the change in temperature one side of the point to the other is dramatic. From memory the Aghullas reaches this point with a speed of somewhere around 4 – 6 knots and the Benguela is doing 6 knots or more.

“Disko Troop says:
September 8, 2011 at 3:38 a
Is the increase in Atlantic temperatures involved in the continuing low level of arctic summer ice? Is there much heat transport across the Equator?”

I think that is a relevant question as looking at http://ocean.dmi.dk/arctic/meant80n.uk.php there is not a lot of evidence of a warmer atmospheric summer temperature over the Arctic in 2011 and yet we will probably experience 2007 ice extent minimum this month. So the reduced summer ice must be due to wind and currents.

“David Smith says:
September 8, 2011 at 4:49 am
Distribution of heat is important. Warmer Atlantic water in the near-Arctic regions means greater evaporation there. The greater evaporation places greater amounts of water vapor into the Arctic atmosphere. That increase may, via water vapor’s greenhouse effect, trap more heat in the Arctic and thus raise the atmospheric temperature. Perhaps some of the observed higher temperatures in the Arctic are due to this.”
Problem is there seems to be little evidence of increased summer temperatures as per http://ocean.dmi.dk/arctic/meant80n.uk.php if DMI’s recordings are in the “ballpark”. Ultimately it must be boil down to wind and currents transporting warmer water in or blowing ice south thus increasing the smelting compared with the multiyear average. Furthermore it is common knowledge that 9/10 of floating ice is below sea surface giving water a much larger area to work on.

I believe Fig 1A is a good example of why so many people (the ‘ignorant public who just don’t understand’ /sarc) mistrust much of climate science. The obs go from ~2×10^22 J in 1990 to ~6×10^22 J when the series finishes in late 2000’s: delta ~4×10^22J. EXP_REM (red) goes from ~2.4 x 10^22J to ~4 x 10^22J over the same period, delta <2×10^22. EXP_CTR (green) goes from ~4 x10^22J to ~6×10^22J, delta ~2×10^22J. Watt the? The best models get half the recent trend? Damn those pesky observations.

If's that's the best we can do why would anyone think we understand the system? Sure, you might be able to argue it's interesting science, but science with foundations secure enough to drive policies that affect the lives of billions? Science worth taking a share of the taxpayers dollars that can't then be used on other priorities and threats? Do scientists REALLY not understand why the public is becoming anti-science?

Geographers argue about where the Atlantic and the Indian Oceans meet. I confirm what others have said above – they meet at the tip of the Cape Peninsular as anyone who has bathed both sides of it will tell you. Sardines spawn south of the Cape annually and immediately swim north sticking assiduously to cold water. The vast bulk of them turn left at Cape Town and stay in the cold waters of the Benguela.
A small minority (still in the trillions) are fooled by the weak and very narrow counter current that runs northwards along the east coast. Hence these misguided fellows get trapped in a strip of cooler water which averages only two hundred yards or so wide. From my veranda in early June you may see what looks like a thunderhead above the shoreline. This is in fact a zillion sea birds that have flown all the way from the Cape to feast on the Sardine Run. The sardines are literally herded by thousands (not an exaggeration) of dolphins along with sharks and other carnivores. The Natal South Coast Sardine Run is one of the sights of the world.

The moral of the story is, if you are a sardine, keep left at Cape Town in the cold Benguela Current.

Is the notion of increased ocean heat content consistent with the Argo findings? Hasn’t Argo been reporting that ocean heat content is relatively constant over the period it has been in operation. That global temperatures have been relatively unchanged for the past 13 years – in effect the climate has stopped changing.

Coincidentally this was about the time skeptics started watching over the shoulders of the scientists that were reporting rapid global warming/climate change/climate disruption. About the same way a watched pot never boils. So it seems that the way to stop global warming is not to eliminate CO2. It is simply to have skeptics check the figures.

Thus,global warming was solved not by spending trillions of dollars to blast industrial economies back to the horse and buggy age, but rather by the power of skepticism.

In results of a study published in this week’s issue of the journal Nature, a team of scientists led by University of Miami Rosenstiel School of Marine & Atmospheric Science Oceanographer Lisa Beal, suggests that Agulhas leakage could be a significant player in global climate variability.

…
Recent research points to an increase in Agulhas leakage over the last few decades, caused primarily by human-induced climate change.

The finding is profound, oceanographers say, because it suggests that increased Agulhas leakage could trigger a strengthening in Atlantic overturning circulation–at a time when warming and accelerated meltwater input in the North Atlantic has been predicted to weaken it.

“This could mean that current IPCC model predictions for the next century are wrong, and there will be no cooling in the North Atlantic to partially offset the effects of global climate change over North America and Europe,” said Beal.

ferd berple says:
September 8, 2011 at 7:04 am
Is the notion of increased ocean heat content consistent with the Argo findings? Hasn’t Argo been reporting that ocean heat content is relatively constant over the period it has been in operation. That global temperatures have been relatively unchanged for the past 13 years – in effect the climate has stopped changing.

Coincidentally this was about the time skeptics started watching over the shoulders of the scientists that were reporting rapid global warming/climate change/climate disruption. About the same way a watched pot never boils. So it seems that the way to stop global warming is not to eliminate CO2. It is simply to have skeptics check the figures.

Thus,global warming was solved not by spending trillions of dollars to blast industrial economies back to the horse and buggy age, but rather by the power of skepticism.

If we could get climate scientists to show their work, we may eliminate a century of global warming. Seriously, I think it’s that bad. Poor siting of stations, bad station bad, unjustified adjustments to the data, poor accounting for UHIE and secret computer code all make for a lot possible overstatement of warming.

“A surface-forced global ocean-ice coupled model is used to test this hypothesis and to find that the observed warming trend of the Atlantic Ocean since the 1950s is largely due to an increase in the inter-ocean heat transport from the Indian Ocean.”

Ahhh, now I see: This could mean that current IPCC model predictions for the next century are wrong, and there will be no cooling in the North Atlantic to partially offset the effects of global climate change over North America and Europe, this supports an AR5 tipping point. Let me presage that section for policy makers: ” Recent oceanographic data in published, peer-reviewed work related to ocean currents suggests that the predicted cooling effects of a colder North Atlantic used in past scientific reports (see AR4) may not be available to counter-act European and North American warming trends; while further research is needed, prudence demands an increased level of risk be assigned to the potential for disastrous warming.”

I like to point out that there is a another slow process, which will have an impact on sea currents and consequently on climate changing patterns.
That would be the constant but small shift of the continental plates to the north. We know that Africa pushes against Europe and also Arabia. At the collision zone we have earthquakes and volcanic activity (for example the eastern Africa rift zone).
But what happens south of Africa? The African plate (and land mass) moves north and leaves an ever widening opening for the waters behind.
Yes, it is a slow process, which the graph “Figure 2B time series of the simulated AMOC index” nicely indicates. We will get more exchange between the Indian ocean and the Atlantic ocean so to speak!
Will the shifting plates or the changing currents have an impact on the Gulf stream? Only the future will tell…

I have serious reservations about oceanographic statistics of this nature prior to 1957, the commencement of the International Geophysical Year.That was when information became consistently reliable, with vast improvements in instrumentation and standards of measure.

The recent La Nina events might be quite different than events of the recent past if the cosmic ray / cloud production hypothesis is correct. Generally during a La Nina event, there is reduced cloud cover over the equatorial region of the Pacific along with strong trades. This pushes sun-warmed water into the Western Pacific and Indian oceans. If we have cloud cover that is greater than would normally be seen during such an event, the temperature of the water pushed West by the stronger trades might be reduced.

This period of La Nina conditions coupled with a weak solar cycle might unfold in an interesting way. We will just have to wait and see. It could be that the Indian ocean might not respond as it has in the recent past. This graph from Tisdale’s latest posting:

shows that the Western Pacific and Indian Oceans haven’t really warmed from a 1998 step up. The Indian Ocean by itself has apparently warmed since 2008:

son of mulder says: “So does this increase in heat correlate with annual Atlantic storm energy, or any other hypothesised destructive consequence of CAGW? Because looking at this
it appears not.”

On a centennial timescale, it appears to be uncorrelated with ACE. But try mentally picturing it with out the long term upward trend: it looks sort of like an inverted “AMO”, right? “AMO” is correlated with ACE.

Correlatiton does not equal causation, and one small set of data in an intensely chaotic system is not enough to either validate or invalidate their proposed theory. Give it another couple decades of observation before trying to cobble a theory together out of every field observation. Sometimes data doesn’t suggest a theory. Is there ever a paper these days where they find that “no conclusions can be drawn at this time”? Not often. Isn’t that curious?

A surface-forced global ocean-ice coupled model is used to test this hypothesis and to find that the observed warming trend of the Atlantic Ocean since the 1950s is largely due to an increase in the inter-ocean heat transport from the Indian Ocean.

I’m with JJ. How can you possibly test an hypothesis with a computer model? Are we stuck in the Matrix or something?

Bob Tisdale says:
September 8, 2011 at 1:52 am
Variations in Agulhas leakage may explain some of the difference between the South Atlantic and Indian Ocean OHC, and would help to explain why South Atlantic OHC has flattened in recent years…
…while the Indian Ocean OHC has continued to rise:

But it does not explain why the rise in North Atlantic OHC was double that of the South Atlantic and almost 4 times higher than the Indian Ocean:
It also does not explain why North Atlantic OHC has dropped so drastically since 2005:

May be rainfall could help to find an explanation. The change in atmospheric dynamic due to the others anticyclonic zones, as Açores, Norway, Islande, etc. which drive the wind ways and so the rainfall and above all the monsoon.

Monsoon could explain why Indian ocean is cooler and North Atlantic hotter.

When rain fall down into Indian ocean it doesn’t fall into North Atlantic by this way one ocean is cooler than the other. When moonson is important in Indian Ocean weather is dry in north Atlantic wich receive no rainfall. I think the absence of rain is the best explanation for the positive anomaly of the north Atlantic. Sun heat the ocean and the lake of rainfall can’t get it colder.

It’s my explanation by studying for a long time how winds and atmospher are so changing in relation with solar activity (Albert Nodon in France was a precursor for this subject ;)

So does this increase in heat correlate with annual Atlantic storm energy, or any other hypothesised destructive consequence of CAGW? Because looking at this
it appears not.

Following the ACE chart image, I found the annual data and plotted it (nothing like what Bob T or anyone else does!), because it looked like the peaks were about as (ir)regular as the sunspot graphs we see all the time.

It turns out the average “ACE Maxima” is right at 5.00 years (with some very small subjectivity on what makes a peak). Some of the maxima are much lower than others, as is the case for sunspots, but peaks they are.

This cannot have gone unnoticed.

But your point, son of mulder, I agree with: This study’s purported increase in Atlantic heat energy should be resulting in increased cyclonic activity, according to my understanding of the part heat plays in the genesis of hurricanes. Instead, all we see from the ACE is four peaks in 1995, 1998, 2005 and 2010 that are very similar to an earlier grouping of “maxima” in 1950, 1955, 1961 and 1964. The hockey stick doesn’t appear in the ACE at all. One would expect SOME correlation. 1950-1964 is dead in the middle of the “handle” of their hockey stick.

So, for those here who point out “Hockey stick!” I’d tend to agree with them… If heat energy has anything to do with hurricane formation and intensity (and we know it does), one would expect it to show up in the ACE, too. So, IMHO, it is proper to wonder if their models and methodology are not amiss. The hockey stick blade just doesn’t exist in the ACE. as you pointed out, son of mulder.

I think that is a relevant question as looking at http://ocean.dmi.dk/arctic/meant80n.uk.php there is not a lot of evidence of a warmer atmospheric summer temperature over the Arctic in 2011
———
John I followed the link and all I can say, in the face of a graph showing above average temperatures leading up to the melt season, is that you have a novel idea of what constitutes “little evidence”.

“So, IMHO, it is proper to wonder if their models and methodology are not amiss.”

There was a time when I was fairly new to the climate discussion when I learned about AMOC and immediately found it to be an “easy” way of conceptualizing AMO variations. However, I’ve had a few more years since then to explore geophysical data a lot more carefully. Observation suggests AMOC ≠ AMO. It’s human imagination & resulting computer modeling fantasies that push the notion that AMOC = AMO, largely because academics engaged in abstract misconception have overlooked some sampling theory fundamentals about how Earth spatiotemporally aliases solar pattern [spatiotemporal version of Simpson’s Paradox].

“Related articles could have been written on All India Rainfall Index & other variables, but the audiences’ handle on the solar, lunisolar, & spatiotemporal nature of interannual variations was revealed to be inadequate in comments here […] https://wattsupwiththat.com/2010/10/11/atlantic-hurricanes-the-sun/ “ [Atlantic Hurricanes & the Sun]

Above I see some refreshing comments from Patricia R (September 8, 2011 at 3:07 pm). The problem is that people try to conceptualize climate using anomalies. Hydrology’s a function of ABSOLUTES, not anomalies.

Patricia R offers an excellent tip for Bob Tisdale. I would encourage readers to study variation of annual surface wind patterns in the North Indian Ocean while keeping this [ http://upload.wikimedia.org/wikipedia/commons/d/d7/ITCZ_january-july.png ] in mind. And to reiterate a cautionary note: It’s NECESSARY to consider SEASONAL evolution. (More details another day…)

“Related articles could have been written on All India Rainfall Index & other variables, but the audiences’ handle on the solar, lunisolar, & spatiotemporal nature of interannual variations was revealed to be inadequate in comments here […] https://wattsupwiththat.com/2010/10/11/atlantic-hurricanes-the-sun/ “ [Atlantic Hurricanes & the Sun]

I didn’t read your article before. Thank you for the link !
I see we are on the same argument ! the best one, of course !

The problem is that people try to conceptualize climate using anomalies. Hydrology’s a function of ABSOLUTES, not anomalies.”

The debate is about climate change not simply climate and so anomolies, size, frequency patterns and impact, are what characterise change and help one identify change. All science is ultimately about absolutes but even in the case of hydrology change is identified by anomolies.

Clearly, the Indian Ocean warming is caused by too many people swimming in this ocean. But when they exit the ocean, the evaporation of the water on their bodies will cool the earth, thereby making it WARMING-NEUTRAL. In the worst case, residents could be required to empty their ice cubes into the ocean to offset the warming, However, if the ocean starts to cool too much, people will have to do more swimming in that ocean, or immerse waterproof heaters that will be sold by cap-and-trade outfits.

“EOP, which are integrated globally, are the arbiters of terrestrial climate disputes. In light of the preceding observations, popular theories speculating that AMOC drives AMO (& so-called “60 year cycles” more generally) should be brought under scrutinizing review. Also, we now have a new basis (similar to the double-helix of DNA) for reframing & refining our spatiotemporal conceptions of interannual variability.”

Paul Vaughan I read your page about LOD and luni-solar cycles. Leif Svalgaard always repeat the same “it’s only graphs with no scientific demonstration” he is right in the essence.
I have the same matter. Sure I need courage and accept your encouragements.
Did you try to postulate to IPPC panels ? it was possible during a time ! May be you could find some scientists which could find a scientific demonstration.